Location: Meat Safety & Quality Research
Title: Effect of degree of dark cutting on tenderness and flavor attributes of beef Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 30, 2013
Publication Date: June 16, 2013
Citation: Grayson, A., Shackelford, S.D., Mckeith, R., King, D.A., Miller, R., Wheeler, T.L. 2013. Effect of degree of dark cutting on tenderness and flavor attributes of beef. [abstract] Reciprical Meat Conference. p. 72. Technical Abstract: The objective of this experiment was to determine the effects of degree of dark cutting (DC) on tenderness and flavor descriptive attributes of beef. During routine grading procedures at a large-scale U.S. beef harvesting facility, DC carcasses (n=160) and matching normal cohorts (NC; n=160; same production lot and similar marbling level as each dark cutter) with normal lean color were selected for the study. Longissimus lumborem (LL) pH was determined online and DC carcasses were classified as severe DC (SEDC; mean pH=6.9, n=40), moderate DC (MODC; mean pH=6.6, n=40), mild DC (MIDC; mean pH=6.4, n=40) or shady DC (SHDC; mean pH=6.1, n=40). Mean pH for NC was 5.66. Not all of the DC carcasses were ungraded (No Roll) carcasses. In fact, for SHDC less than half of the carcasses were No Roll. The number of carcasses in each of the classes graded Certified Angus Beef, U.S. Choice, U.S. Select, and No Roll was 0, 1, 3, and 36 for SEDC; 0, 2, 3, and 35 for MODC; 0, 6, 8, and 26 for MIDC; 0, 6, 16, and 18 for SHDC; and 8, 83, 67, and 2 for NC. Vacuum-packaged strip loins (LL) were obtained from the left side of each carcass and aged (2°C) to 14 d postmortem. One steak (2.54 cm) was collected for fresh 14 d slice shear force (SSF). A 6 cm section was frozen and used for trained descriptive flavor and texture sensory evaluation (2, 2.54 cm steaks per section). Statistical analyses were completed using PROC GLIMMIX in SAS. Slice shear force was higher (P<0.05) for SHDC (251 N) and MIDC (225 N) than MODC (190 N), NC (174 N), and SEDC (165 N). Sarcomere length was shorter (P<0.001) for all DC classes (1.66, 1.67, 1.71, and 1.73 µm for SEDC, MODC, MIDC, and SHDC, respectively) than NC (1.86 µm). Additionally, sarcomere length was shorter for SEDC and MODC than SHDC (P<0.01). Western blotting of desmin to assess the extent of postmortem proteolysis at 14 d postmortem indicated that samples from NC had approximately 10% more proteolysis than all DC classes (P<0.05). Trained sensory panel ratings for tenderness (8=extremely tender; 1=extremely tough) differed (P<0.05) among each class and indicated that SEDC was most tender (6.5), MODC (6.1), MIDC (5.2), and NC (4.9) were intermediate, and SHDC was least tender (4.7). Panelist scores for tenderness did not agree with SSF and could be attributed to sensory panel samples being frozen (and subsequently thawed) prior to evaluation. Juiciness ratings (8=extremely juicy; 1=extremely dry) differed (P<0.05) among each DC class (5.9, 5.7, 5.4, and 5.2 for SEDC, MODC, MIDC, and SHDC, respectively). Despite differing in pH, juiciness was similar for SHDC and NC. Fat flavor scores increased from NC progressively through the DC classes as pH increased (1.4, 1.6, 1.9, 2.0, 2.2 for NC, SHDC, MIDC, MODC, and SEDC), with NC and SHDC differing from MODC and SEDC (P<0.001). Musty flavor scores were higher (P<0.001) for MODC and SEDC than other groups. In accordance with the pH differences, all DC classes had lower sour flavor scores than NC (P<0.001). This study shows DC and NC carcasses differed in LL tenderness, juiciness, and flavor attributes and the direction and/or magnitude of those differences varies greatly depending on the severity of DC. Steaks from DC with intermediate pH (SHDC) are most likely to be tough, yet many of these carcasses are included in routine U.S. Select and U.S. Choice product lines.